1. FIELD OF THE INVENTION
The present invention relates to a method for transporting hot-rolled wire rod and an apparatus therefor.
2. Decription of the Related Arts
Among method of direct patenting of high-carbon wire rod, a method of air patenting by the use of air-blast holds the leading position. However, since a cooling capability of the air-blast in the air patenting is low, a high strength and a high ductility cannot be added to wire rod as in a lead patenting carried out in an off-line.
To increase the cooling capability of the air-blast, a mist-cooling method is proposed. A method wherein an air-blast mist produced by mixing water with the air-blast is used, a method wherein mist produced by spraying water is used, and the like are pointed out as the mist cooling method. However, the side edge portions of rings of wire rod, which is transported in a state such that said wire rod is in the form of continuous series of loops, in the direction of the width of a conveyer overlap each other. If the rings of wire rod which overlap each other are not shifted one from another, the wire rod is not uniformly cooled and there occurs a deviation of strength and ductility of the wire rod. In consequence, the wire rod which can be put to practical use cannot be manufactured.
A method, wherein conveyer rollers are arranged at a certain interval, diameters of both ends of one end of the roller at every several rollers are made large and wire rod is cooled by moving up-and-down the side edge portions of wire rod, is disclosed in a Japanese Utility Model Application Laid Open No. 58839/74. A method, wherein the side edge portions of wire rod are moved up-and-down by means of an eccentric roller, also is disclosed in a Japanese Utility Model Application Laid Open No. 58838/74. Those methods are, however, substantially not effective in mist cooling of the wire rod when time of separation of the rings of wire rod one from another is short and a cooling rate is from 15.degree. to 30.degree. C.
An air patenting method as shown in FIG. 10 is disclosed in a Japanese Patent Application Laid Open No. 15609/74. In this method, vertical rollers 12 are alternately arranged at a predetermined interval on side walls 11 of conveyer 10. Wire rod 13 is moved in zigzags by the vertical rollers 12. The wire rod 13 is cooled by air during its movement.
The method disclosed in the Japanese Patent Application Laid Open No. 15609/74 has, however, the following problems:
(a) When the wire rod 13 is about to be cooled uniformly by making large a shift of the center of a ring of the wire rod 13 from a center line of a conveyer 10, resistance of the wire rod 13 during its transportation grows large in a position of vertical roller 12 which pushes in the wire rod 13 toward the center line of the conveyer.In consequence, since a ring pitch of the wire rod 13 in a push-in position of the wire rod 13 becomes small, a rate of cooling of the wire rod 13 decreases. Hereinafter, the shift of the center of wire rod 13 from the center line of the conveyer is referred to as an amount of zigzag movement. Accordingly, the amount of zigzag movement of the wire rod 13 cannot be increased.
(b) Since intervals among the vertical rollers 12 are made small, the resistance, with which the wire rod 13 meets, grows large and the ring pitches of the wire rod grow smaller. The rate of cooling of the wire rod 13 decreases at a rate of decrease of ring pitches. Therefore, the intervals among the vertical rollers 12 have to made large to some extent. Since the rate of cooling of the wire rod 13 is small in the case of the air patenting and a length of a cooling zone can be made large, an object of cooling of the wire rod 13 can be accomplished even though intervals among the vertical rollers 12 are large. However, when the rate of cooling of the wire rod 13 is large as in the mist cooling, only several vertical rollers 12 are arranged since the cooling zone has a small length of about 10 m. Accordingly, the number of the zigzag movements of the wire rod 13 are approximately twice or three times.
(c) Although the center of the wire rod 13 is shifted from the center line of the conveyer by means of the vertical rollers 12, the rings of the wire rod 13 are transported in a state of being overlapped and there is no portion where the wings of the wire rod 13 are shifted one from another. Accordingly, nonuniformity of cooling of the wire rod is produced.
(d) The ends of the wire rod 13 have not ring shape, but irregular shapes. Therefore, when the vertical rollers 12 are used being exposed, the end portion of the wire rod is caught by the vertical rollers 12. In consequence, the wire rod 13 cannot often be transported smoothly.